The present invention relates to a NTC thermistor material which is made using MnCO.sub.3 --NiO--CuO--ZnO--Co.sub.3 O.sub.4 --Fe.sub.2 O.sub.3 --TiO.sub.2 as the basic composition.
Generally, a thermistor is a kind of semiconductor which exhibits very great and non-linear resistance variation in response to temperature change, and which is manufactured by mixing oxides of iron, nickel, manganese, molybdenum, and cobalt and then sintering thereof.
The metal oxide group thermistor manufactured using a transition metal oxide is a semiconductor element in which the electric resistance decreased exponentially in response to temperature change. Since there is a great difference in crystal structure and sintering characteristics in accordance with its raw material ingredients or sintering temperature, it exhibits a great difference in standard temperature resistance and resistance variation in response to temperature.
Such metal oxide group thermistors are widely used as a temperature sensing element, temperature compensating and controlling elements, as an essential element of various precision measuring and analyzing instruments including voltage controlling elements.
In conventional metal oxide group thermistor material, the manganese-nickel-cobalt-copper group which is a spinel group and the iron-titanium group which is a hematite group are generally used. In the case of former spinel group thermistor, it exhibits a wide resistance range and great B constant according to its composition, and therefore it is widely used. [Ref.: 1. Thermistors (ed. by E. D. Macklen), Electrochemical Pub., Ayr. Scotland (1979). 2. Semiconducting temperature sensors and their application (e. by H. B. Sachse), John and Wiley, New York (1975). 3. Ceramic Materials for electronics (ed. by R. C. Buchanan), Marcel Dekker, New York (1986)].
However, in making the manganese-nickel-cobalt-copper group thermistor, the price of cobalt oxide is very high, which results in a disadvantage in manufacturing cost. Also when copper oxide is absorbed, it has problem of generation of environmental pollution during manufacturing of the thermistor [Ref.: Hawley's condensed chemical dictionary, 11th edition (ed. by N. L. Sax and R. J. Lewis, Sr.), Van Nostrand Reinhold Co., New York (1987)].